Environmental Protection Agency Administrator Gina McCarthy said she is confident the Obama administration's cornerstone climate regulation that would limit power plant carbon emissions will survive an expected legal challenge.

Her comments at a Washington event hosted by the Christian Science Monitor on Tuesday come a week after the Supreme Court sent an EPA rule limiting mercury and other toxic air pollutants back to a lower court. The high court found in a 5-4 decision that the agency didn't properly consider the costs before crafting the rule.

"The court seemed to go out of its way to narrow this decision in many ways," she said.

McCarthy noted the ruling on the mercury regulation didn't reject the EPA's ability to regulate emissions, nor did it vacate the rule. She said the tailored approach left her certain that the EPA would be able to defend its proposed carbon rule in court.

"We certainly know how to defend lawsuits, for crying out loud. The Clean Power Plan will absolutely be litigated," McCarthy said. "We actually are very good at writing rules and defending them, and this will be no exception."

The EPA carbon proposal, known as the Clean Power Plan, aims to cut electricity emissions 30 percent below 2005 levels by 2030. EPA plans to finalize it this summer, a move that President Obama will use to buoy the United States' role in international climate talks set to begin in Paris in late November.

Conservatives oppose the rule, saying it would raise electricity bills and kill coal-mining jobs. Some also have questioned its legality, and Senate Majority Leader Mitch McConnell, R-Ky., has urged states not to submit a plan to comply. Some states have warned they won't, though just one — Oklahoma — has taken action to prevent compliance.

McCarthy said the EPA could enforce a federal plan on states if they don't comply with the rule.

But some experts contend the agency has legal authority to enforce changes in state energy emissions through only two of four so-called "building blocks" — improving power plant efficiency and converting generation from coal to natural gas. The EPA also believes states can lower emissions by adding renewable energy and boosting customers' energy efficiency.

McCarthy wouldn't comment on whether she thinks the agency could call on emissions cuts through renewable energy and customer energy efficiency, as she said there would be significant changes between the proposed and final version of the rule.

"I can't really speak to any specific outcome other than I know there are going to be changes," McCarthy said. "I don't think it's worthwhile to go through each of the building blocks at this point."